Microsoft is giving free licenses for Windows 7 Beta. So no need to use any Crack. It is simple.
You need windows live id for this. if you have a hotmail address, that can be used as a live id. Otherwise create one. (you can get @hotmail.com, @live.com, @live.in etc as your email address if you are creating one. There is also a chance that you can get yourname@live.com, just give it a try)
1. Go to http://live.com
2. Sign in with your windows live id
3. Go to Get the Beta (On the same browser)
4. Choose which version you need (32 bit or 64 bit) and language from the corresponding dropdown.
5. It may ask for password again, enter the password of your windows live id
6. If they ask for some details enter it
7. It will redirect you to the download page with registration key and download link
Or you can use the method which is described in the following link check this link